DESCRIPTION: The studies proposed here seek to contribute to the understanding of how the human brain processes and maintains the sounds of spoken and written words. A secondary goal is to investigate how focal brain injury changes normal brain activity during phonological processing. The primary method to be used is functional Magnetic Resonance Imaging (fMRI), which shows patterns of relative regional brain activity associated with the performances of specific cognitive operations. Results of these studies will help resolve conflicting data from previous studies, will test hypotheses concerning neural substrates associated with spoken and written word processing under different memory requirements, and will provide a basis for studying the effects of focal brain lesions on phonological processing. Separate sets of experiments will address three specific aims. One set of experiments aims to identify the brain regions involved in activating phonological information from the auditory and visual modalities. These studies will provide evidence of differences in phonological processing during the course of listening to or reading words and nonwords. A second set of studies will address the contribution of specific task requirements to neural activation differences that have been reported for phonological processing, specifically examining the contribution of orthographic effects and verbal working memory processes. These experiments will assess the neural consequences of the need for phonological information to be maintained over time, and will test the hypothesis that spoken and written sources of word sound information require different levels of involvement of articulatory processes in word maintenance. The third set of studies uses fMRI methods to explore phonological processing in patients with focal brain lesions and resulting aphasia. These studies will determine how the functional neuroanatomy of phonological processing differs when phonological tasks can be performed with high levels of accuracy compared to when performance is impaired, thus attempting to understand the nature of selective deficits of phonological processing. The ultimate goal of these studies is to provide detailed information about the neural bases of a variety of potentially separate processes involved in the activation and maintenance of phonological information under different conditions. Better understanding of neural bases of phonological processes and of the effects of brain damage on those processes may provide a basis for improved therapies for aphasic symptoms.